Braking system for hoists and the like



Oct. 16, 1962 L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7Sheets-Sheet 1 ATTORNES Oct- 16, 1962 e. L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE '7 Sheets-Sheet 2 Filed March 3,1959 Oct. 16, 1962 G. TlLEY ETAL BRAKING SYSTEM FOR I-IOISTS AND THELIKE '7 Sheets-Sheet 3 Filed March 5, 1959 W0 0 OJ I Oct. 16, 1962 G. L.TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7Sheets-Sheet 4 INVENTORS GERALD L. TILEY ERIC OLDFIELD GERALD W. WYKES1962 G. L. TILEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March :5, 1959 7Sheets-Sheet 5 INVENTORS GERALD L.TILEY ERIC OLDFIELD B GERALD W.WYK E$auw nmnuns Oct. 16, 1962 G. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7Sheets-Sheet 6 1'. iii Fig 6 5% N F13 F! EFW 472" Im" L MAN! 52BINVENTORS GERALD L.T|LEY ERIC OLDFIELD GERALD W. WYKES Oct. 16, 1962 G.L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7Sheets-Sheet 7 y s II W'll I INVENTORS GERALD L.T|LEY ERIC OLDFI ELDGERALD\W. WYKES M? WATTORNEYS ite tare BRAKING SYSTEM FOR HGISTS AND THELIKE Gerald L. Tiley, near Hamilton, ()ntario, and Eric Oldfield andGerald W. Wykes, Burlington, Ontario,

Canada, assignors to Canadian Westinghouse Company Limited, Hamiiton,Qntario, Canada, a Canadian company Filed Mar. 3, 1959, Ser. No. 796,906Claims priority, application Canada Mar. 4, 1958 Claims. (Ci. 188-106)The present invention is concerned with improvements in or relating tobrakes, and especially but not exclusively to brakes such as are usedfor mine hoists.

The movements of the skip or cage of a hoist are usually controlled bymeans of a drum of relatively large diameter, which may be a windingdrum on which the hoist rope is wound, or a driving drum over theperiphery of which the hoist rope passes to be driven by friction. Toobtain eflicient operation of the hoist it must be possible toaccelerate it rapidly to its maximum speed and then decelerate itrapidly to rest. Owing to the large forces involved it is usual practiceto employ the motor as a brake, but brakes must also be provided forstopping the hoist accurately at a level, for holding the hoiststationary while the motor is not operative, and also as an emergencysafety device in case of failure of the motor to act as a brake.

It is an object of the present invention to provide a new brakeconstruction.

It is a further object of the present invention to provide an improvedactuating system for a brake.

According to the present invention there is provided a brake comprisinga pair of brake arms mounted for pivoted movement, a pair of brake shoeseach mounted by a respective brake arm and .engageable with a memberdisposed between the brake shoes on opposite sides thereof to applybraking pressure thereto, first means for moving the brake arms to movethe shoes into engagement with the said member, and a gravity-actuatedweight constituting second means for so moving the brake arms and apneumatic control system.

A specific embodiment of the invention will now be described, by way ofexample, with reference to the ac companying diagrammatic drawingswherein:

FIGURE 1 is a view in side elevation of part of the Koepe wheel of amine hoist and two of the four brakes associated with the wheel,

FIGURE 2 is a View of the apparatus of FIGURE 1, taken in the directionof the arrow 2 in FIGURE 1,

FIG. 2a is a view in section taken along the line 22 of FIG. 2,

FIGURE 3 is a plan view from above of one of the brakes, drawn to alarger scale than FIGURES 1 and 2,

FIGURE 4 is a schematic diagram of the pneumatic equipment of one brakecontrol system,

FIGURE 5 is a schematic diagram of the pneumatic equipment of anotherbrake control system, and

FIGURE 6 is a schematic diagram of the electrical equipment of the twobrake control systems.

FIGURE 6A is a diagrammatic representation of the electromagneticactuators and their associated contacts and fluid relays.

Referring now to FIGURES 1 to 3 of the drawings, a Koepe drum consistsof a central rope receiving part 10 and two radially extending rims 11,and is provided with four disc brakes, each generally indicated by 12,each rim serving as the disc for two of the brakes. The drum is mountedby means of a shaft 13 between bearings 14 and is rotated as required bya hoist motor (not shown) connected to the shaft 13 through a suitablecoupling (also not shown). The bearings 14 are in turn mounted on thehoist framework 16 which is fastened securely to the floor 3,58,547Patented Oct. 16, 1962 of the chamber in which the hoist drum, itsbrakes and motor are located.

The two brakes associated with each disc are disposed diametricallyoppositely to one another, each brake comprising a frame, generallyindicated by 17, which is rigidly secured to the hoist framework 16. Twolevers 18 are mounted for movement in a horizontal plane by respectivevertically-disposed pivots 19, which are mounted in a cross member 20 ofthe frame 17. The ends of the levers 18 nearer to the disc 11 areprovided with brake shoes 21, which are pivotally connected to thelevers to accommodate small angular changes as the levers move abouttheir pivots, so that the braking surfaces of the shoes can alwaysremain parallel to the associated braking surfaces of the disc. Eachshoe is provided with a brake lining 22 of a suitable composite frictionmaterial.

The brakes are applied by supplying fluid under pressure, compressed airin this embodiment, to the interior of a respective cylinder 23 which issupported in the frame 17 by cross-members 24. The fluid under pressureenters the cylinder between two oppositely-disposed pistons 25 andforces them apart, so that the immediately adjacent lever ends areforced apart, the pistons engaging their respective arms by means ofcontact members 26 that are axially adjustable to take up wear in thebrake shoes. In other embodiments flexible diaphragms may be employed inplace of the pistons 25, since the distances through which they mustmove to apply the brakes fully is com paratively small. When the pistonsmove apart the brake shoes 21 move together, with a mechanical advantagedue to the greater distance of the pistons from the pivots 19.

The braking effort that is applied by each brake to the drum can becontrolled accurately by controlling the pressure of the fluid withinthe cylinder 23. Upon release of the pressure in the cylinder, e.g. byconnecting the cylinder interior to atmosphere, the brake is positivelydis engaged by a tension spring 27 connected between the arms on thesame side of the pivots 19 as the cylinder 23'.

A safety device whose operation will be described in detail below isconstituted by a weight 28, having a Wedgeshaped part 29 which extendsbetween the arms 18 and is engaged at its narrowest width by two rollers30' mounted respectively in the arms 18 by axles 31. The weight isconnected by a rod 32 to a piston in a cylinder 33, and during normaloperation of the brake the weight is held up against gravity by theaction of compressed air supplied to the interior of the cylinder 33. Ifthe air pressure within the cylinder is insuflicient the weight willdescend, the wedge-shaped part forcing apart the rollers 30 so that thearms 18 are forced apart and the brakes are applied.

In most, if not all, of the applications of such a brake it is importantthat its speed of application is controlled by the inherent design ofthe brake and/ or by its control mechanism. This is especially importantin the case of a safety device. For example, in a Koepe wheel hoist ifthe wheel is braked too violently the hoist rope may slip, and since thesliding friction between the wheel and rope is smaller than thestationary friction, there is a danger that control of the hoist will belost completely.

In a brake in accordance with the invention the speed of brakeapplication by the safety device can be predetermined accurately bychoice of the design for the wedge-shaped part 29, for example by choiceof the con tour of the sloping surfaces engaging the rollers 30. Topermit the correct engagement of the sloping surfaces with the rollers,in some embodiments (as illustrated herein), the wedge-shaped part maybe separate from the main weight 28 and connected thereto by rollers 29Aworking loosely in slots in the weight and/or the part, so that thewedge-shaped part can settle itself correctly between the rollers as itdescends, despite some misalignment of the main weight 28. In otherembodiments the rollers may be replaced by other guiding and engagingmeans, such as sliding shoes, which may be pivoted to the arms 18. p p vEach weight 28 is guided in its descent by a pair of guide rods 28A, themajor lengths of which are a very loose fit in corresponding guidepassageways 283 in the weight. The uppermost part 280 of each rod isenlarged to be a snug fit in the passageway 28B. Thus, when the weightis in its fully raised position the enlarged parts 28C hold the weightagainst tilting, which might cause rubbing of the corresponding brakeshoe against the disc, but after the weight has descended asmalldistance it has cleared the enlarged parts and the danger ofexcessive friction between the weight and rods is reduced, besidespermitting a little tilting of the weight which may be desirable, forexample, when the weight and the part 29 are rigid with one another.

FIGS. 4 and 5 illustrate the pneumatic equipment and the functionalrelations thereof in two diiferent embodiments of the invention.Similarly, FIG. 6 illustrates the electrical equipment which serves toactuate or control the pneumatic equipment shown in FIGS. 4 and 5. FIG.6A is a convenient schematic guide by which one may identify aparticular pneumatic component in either FIG. 4 or FIG. 5 and thenquickly identify the electrical control component in FIG. 6 whichactuates that pneumatic component. For example, in making a correlationbetween pneumatic components in FIG. 4 and electrical components in FIG.6, it is only necessary to align FIGS.

4, 6 and 6A side by side horizontally. Assuming then that one wishes tofind the electrical component in FIG. 6 which actuates a particularpneumtaic component in FIG. 4, say valve 44, it is only necessary tolook at the vertical line numbered 44 in FIG. 6A. One will note that thevalve symbol on this line is at the same level as the valve 44 in FIG.4. Tracing further down this vertical line to the electrical symbol onit, it is only necessary to look horizontally from this latter symbol tofind on FIG. 6 the corresponding electrical component 44. Of course,FIG. 6A can also be used to proceed from a known electrical component inFIG. 6 to the correspondng pneumatic component in FIG. 4. The sameprocedure enables one to correlate FIGS. 5 and 6.

' Referring now to FIGURES 4 and 6 and 6A, the brake control systemillustrated therein employs both pneumtaic elements (circuit of FIGURE4) and electrical elements (circuit of FIGURE 6). The elements in FIGURE4 within the broken line are supplied for each brake,'wl1ile thoseoutside the line are common to all four brakes. The circuit of FIGURE 6is for all four brakes. The compressed air for operating the system issupplied by a compressor (not shown) at about 80-100 pounds per squareinch (p.s.i.)' and is fed through a filter 34' and a lubricator 35 topipe 36. It will be understood that other main supply pressures can beemployed, but this valueis found to be convenient for this particularembodiment. Moreover fluids other than air can be em ployed, forexample, a liquid. Four valves 37 to 40 receive air from the pipe 36,the first three being regulating valves which supply air at a presetoutlet pressure;

in FIGURE 4 this outlet pressure is indicated by the figure in thecentre of the respective valve. The output pressure of the fourth valve40 can be varied from the maximum available to zero by movement of anoper ators handle 41, an outlet 42 of the valve leading to atmosphere.The output pressure of the valve 40 is shown to the operator by a gauge43.

Air from the valve 40 can be fed via valves 44, 45 and 46 connected inseries to a relay'valve 48, the last mentioned valve controlling thesupply of air from the pipe 36 to the brake cylinder 23. Thus, air fromthe pipe 36 is supplied to the inlet F of the valve 48 and is deliveredfrom its outlet G (thence to the cylinder 23) at the pressure of the airsupplied to its inlet E. The function of the valve 48 is to supply tothe cylinder 23 as quickly as possible the relatively large volume ofair required for application of the brake, while permitting the use ofmuch smaller volumes in the remainder of the circuit, so that speedyoperation is obtainable. An outlet H is connected to atmosphere. Each ofthe valves 44 to 46, as well as another valve 47, is of a pressure/solenoid type which is 7 only actuated when the solenoid thereof isenergized and a preset actuating pressure is applied to the inlet portD; when the valve is actuated the ports C and A are con-. nectedtogether and when it is released the ports B and A are connectedtogether. A valve 49 operates when actuated and released in the same wayas the valves 44 to 47, but for actuation requires only the applicationof air to inlet D at a preset pressure suflicient to cause fullapplication of the brakes. The function of the other elements of thecircuit will be described as necessary.

' In describing the operation of the system it will be assumed at thestart that the hoist is shut down and there is no air supply, the brakesbeing applied by their weights 28. It is also assumed that the hoist wasleft in condition for automaitc operation, so that the contacts MAN. 1-3are all open. It is a characteristic of this brake operating system thatonce the brakes have been applied by the weights they can only bereleased by the intervention of the operator.

' The application of electrical power to the system between terminals Land N has no effect, since the supply of power to the valves etc. isblocked by open contacts 50A of main relay 50; the operating winding 50cannot be energized until the contacts of a timmgrrelay T and varioussafety devices have been closed or short-circuited. Some of these safetydevices, for example, are weight limit switches 51 having contacts 51Athat are only closed when the associated weights have been raised fully.Operating winding 52 cannot be energized owing to the open contacts 53Athat are closed only when full braking air pressure is applied to apressure-operated switch 53. At this time the valve 44 is released andthe switch 53 is connected to atmosphere via port 44B.

' If the compressor is now started air at supply pressure is supplied tothe valve 37 to 40, to the ports 44D and 47D and to the relay 48. Theair supplied from valves 37, 39 and 40 is blocked by the unactuatedvalves 49, 46 and 44 respectively, while that supplied from valve 38 toports 45D and 46D is ineffective, since the solenoids of the valves 45and 46 are not energized. No air is supplied-by relay 48 to cylinders23, since the inlet E of the relay is connected to atmosphere via valveport 49C. Thus, although both air and electric power are supplied to thesystem the brakes will remain applied by the weights 28. I

To regain control of the brakes the operator moves the manual/ automaticselector switch to the manual position, closing the contacts MAN. 13;moves the control valve handle 41 to the FULL-ON position; and thenpresses a push-button 54 (FIGURE 6). Provided that the contactsassociated with various safety devices not immediately concerned withthe brakes are closed (indicated herein by the broken line connection inseries with the pushbutton contacts 54A) the pressing of the pushbuttonshortcircuits (among other safety device contacts) the weight limitswitch contacts 51A and timing relay contacts TA, so that main relaywinding 50 is energized and contacts 50A close. Valve solenoids 44 and45 are now energized via closed contacts MAN. 3 and MAN. 2 respectivelyand consequently valves 44 and 45 are actuated. The actuation of valve44 applies the FULL-ON air pressure to the switch 53 and contacts 53Aclose to energize winding 52, causing contacts 52B to close and enablingwinding 55 to be energized via contacts 52B and MAN. 1. Contacts 55A areclosed when winding 55 is energized and.

47 and valves 47 remain released. The energization of winding 55 closedcontact 55C sealing-in the relay 55 so that it is new independent of theoperation of relay 52 and switch 53. Contacts 55B are closed, andcontacts 47E also, the latter remaining closed as long as the valves 47are released, so that Winding T is energized and contacts 51A can now beclosed by the weights lifting (as suming the other safety devices arenot operated) when the pushbutton can be released.

The actuation of the valves 44 to 46 causes the FULL- ON air pressure tobe applied to each valve 48, so that air at full pressure is fed to therespective cylinders 23 and also to the valve ports 49D via theunactuated valves 47. After a delay while volumes 56 and the brakecylinders are filled the valves 49 are actuated and air from valve 37 isfed to the cylinders 33 and the weights begin to lift. The pressure ofthe air from valve 37 is indicated by a gauge 57. Volumes 58 are filledat this time. When all the weights are fully raised all the contacts 51aare closed. If the pushbutton 54 is released before contacts 51A closethe main relay winding 55 is deenergized, opening the contacts 519A, andthe system returns to its original condition.

The weights are now held raised by the air from valve 37 and the rakesare applied under control of the valve 49. If the pressure of the airsupplied to the brake cylinder is too low for full application of thebrakes (in this embodiment below about 60 p.s.i.), then it will be toolow for actuation of the valves 49 and the Weights cannot be raised. Ifthe pressure of the air from the valve 46 is now reduced by moving thehandle 41 the contacts 53A open and relay winding 52 is de-energized,opening contacts 52B and closing contacts 52A so that the valvesolenoids 47 are now energized. Each valve 47 is now actuated andsupplies air from outlet A of valve 49 to the inlet D of that valve, sothat the valve 49 is locked-up in the actuated condition, under thecontrol of the air pressure in the weight cylinders 33 and not that inthe brake cylinders 23. Contacts 47E are now open, but contacts 55Bmaintain the winding T energized, the winding 55 being maintainedenergized by closed contacts MAN. 1 and 550. It will be apparent thatthe operation of the switch 53 prevents the raising of the weight unlessthe manual control is placed FULL-ON.

The operator now has full manual control of the brakes by means of thevalve 49, the brakes being fully released by the springs 27 when the airpressure is zero.

If at any time the operator moves the handle 41 to give full applicationof the brakes the switch 53 closes contacts 53A and winding 52 isenergized, opening contacts 52A and releasing valves 47, so that theinlets D of valves 49 are connected to the respective cylinders 23. Iffull braking pressure is not applied to each cylinder 23 air will escapefrom the reservoir 56 through a leak 59 associated with a oneway valve60, until the pressure at inlet 49D is insuflicient and the valve 49releases, connecting the cylinder 33- to atmosphere through valve outletport 49C. As soon as the pressure in cylinder 33 falls a smallpredetermined amount below the required value a quick-acting valve 6-1operates to connect the interior of cylinder 33 more directly toatmosphere and the respective weight descends and applies the brake. Asthe weight begins to descend its respective contacts 51A open,de-energizing winding 50 and opening contacts 50A so that all the valves44 to 46 are released. The release of the valve 46- associated with thefaulty brake connects volume 58 to inlet E of relay valve 48 and,provided the loss in braking pressure is not due to a fault betweenvalve 46 and the cylinder 23, this reservoir pressure causes the relayvalve 48 to supply air at an operative pressure to the cylinder 23, sothat emergency braking is commenced immediately. Air will escape fromthe reservoir to atmosphere through a leak 62 associated with a onewayvalve 63 and the braking pressure applied to 23 is progressivelyreduced. Each brake is so arranged that its weight will begin to applyan elfective braking etfort when the air pressure efiort is about halfnormal, so that an overlap of braking is obtained, but full air pressureand full weight effort are not applied simultaneously. The control ofthe braking characteristic on such a fault is determined by, forexample, selection of the reservoir 58, the leak 62, and the valve 61and by the structure of the weight, as described above. In someembodiments a choke 67 may be included between one or more of thecylinders 33 and their valves 61 to give further control by choice ofthe choke.

In the case of the brake or each of the brakes that is not faulty thevalves 44 to 57 are released, but the full braking air pressure will beapplied by valve 4-7 to valve 4 and that valve will remain actuate-d,applying the air at full pressure from 37 to both the relay valve 48 andthe weight cylinder 3-3. Indicating apparatus (not shown) ofconventional form will be provided to show the operator which of thebrakes has reverted to weight operation.

The operation at any time of any of the safety devices connected incircuit with the winding Stl will also cause the release of the valves44 to 47 and the consequent full air operation of the brakes by the airsupplied from the valve 37. If on the supply of this air there is not afast enough build-up of air pressure in the cylinder 23, the valve 49will be released and will connect the cylinder 33 to exhaust, causingthe weights to descend, and resulting in an emergency stop.

The hoist may be changed from manual to automatic operation only whilethe cage or skip is at a level and an interlock (not illustrated) isprovided on the manual/ automatic switch for this purpose. With the cageor skip at a level the contacts MSX will be open, and since it will bewithin the creep speed zone the contacts CSR will also be open.

The system is brought into automatic operation by opening the contactsMAN. 1-3, which de-energizes the valve solenoids 44 and 45 and thewinding 55, whereupon contacts SSA open and de-energize valve solenoids46 and 47. As described above such release of all four valves 44 to 47causes application of the brakes by air pressure, and failing that bythe weights.

If the valve 47 associated with any brake fails to release properly itwill not be able to test the pressure in cylinder 23 (i.e. by connectingthe cylinder 23 and inlet 49D) and may give a false indication; in sucha case the associated contacts 47E will not close and, since contacts55B are now open, the relay T will release opening contacts TA andthereby causing all the brakes to be applied. The relay T is of the typehaving a delayed release after de-energization so that the contacts 47Ewill have adequate time to close and the brakes will not be appliedprematurely.

It will be understood that the complete hoist will include aconsiderable amount of ancillary apparatus, for example, apparatus forthe hoist motor, apparatus to permit the selection at any level of thelevel to which the skip or cage is to travel, and a programme controlwith associated weighing devices for determining the most efficientacceleration and deceleration of the skip or cage. Such ancillaryapparatus is not illustrated and it will be appreciated therefore thatthe representation herein of the automatic brake control apparatus bythe contacts MSX and CSR only is a considerable simplification, which isadopted only for ease of description of the present invention.

A signal from the ancillary apparatus to start the hoist results in theclosing of contacts MSX, whereupon winding 55 is energized and contacts55A close to energize valve solenoids 46. The pressure relay 53 isalready released so that contacts 52A are closed and valve solenoids 47are also energized. Valve 46 is actuated and air at 5 p.s.i. is fed fromvalve 39 to the relay valve,

which repeats this pressure in the cylinder 23 and primes the brakeready for immediate application by a higher pressure. The actuation ofvalve 47 applies the pressure in cylinder 33- to port 49D and seals-inthe valve 49. As the cage or skip leaves the creep speed zone the relayCSR is energized and contacts CSR close, energizing valve solenoids 45and actuating valves 45, so that the relay valve 48 is connected toatmosphere at port 44C and the brakes are completely released by thesprings 27.

Limit switches such as 64 are provided for each brake and form part of asafety circuit that will stop the hoist motor if the brakes are notfully removed within a predetermined period (about 15 seconds with thisembodiment) after power has been applied to the motor. During travel ofthe skip or cage between levels its speed will be determined by theancillary apparatus referred to above.-

As the skip or hoist enters the creep speed zone at the new level thecontracts CSR open again, releasing valves 45 and applying the primingpressure to the brake cylinders 23. When the new level is reached thecontacts MSX open and winding 55 is de-energized, causing release ofrelays 46 and 47 and application of full braking pressure from valve 37to relay valve 48 and thence to cylinders 23. The valves 47 operate asdescribed above to check that this pressure has been applied to thebrake cylinders and the contacts 47E operate, also as described, tocheck that the valves 47 have operated correctly.

If supply pressure is lost while the hoist is in motion (eg due tocompressor failure or a burst pipe) the valve 47 is released, since itsactuating air pressure is taken directly from the pipe 36. Since therewill be little or no air pressure in the cylinders 23, the valve 49 willalso release and the weights will descend to apply the brakes. The relay50 has contacts (not shown) included in the hoist motor circuit thatwill cause the motor to be stopped upon the opening of any pair of thecontacts 51A, or of any of the other contacts in series With the relaywinding 50. 'It supply pressure is lost while the hoist is at rest withthe brakes on, the valves 47, 49 and 37 will tend to maintain the airpressure at its operative Value; leakage from the system will reduce thepressure applied to 491) until the valve releases and the Weightsdescend. 7

Another set of limit switches 65 are provided for the brakes to detectwear in the brake shoes, these switches having contacts (not shown) inthe hoist motor circuit that stop the motor if the wear is excessive.

The ancillary apparatus is so arranged that on automatic operation, whenthe skip or cage is to be jogged accurately into position at the level,the brake cylinders are kept primed to allow quick and quiet applicationof the brakes. The limit switches 64 are unable to distinguish betweenfull and primed brake application and if the hoist is operating with thebrakes primed for more than about 15 seconds, the timing devicedescribed above will operate and stop the hoist. This is prevented byproviding a pressure switch 66 that detects the relatively low primingpressure and prevents operation of the tim ing device during the joggingoperation.

Referring now to FIGURES and 6 and 6A, components common to the circuitsof FIGURES 4 and 5 are given the same reference and, to avoidrepetition, the differences between the two circuits will 'be described,since the circuits otherwise function in the same manner.

In the circuit of FIGURE 5 the control valve 40 is provided with anelectric interlock switch in the line between contacts operated by a camon the shaft that carries the control handle 41. This switch is inseries with the contacts 52A and is normally closed unless the handle 41is put into the full brake application position. The interlockswitchtherefore performs the same function as the pressure switch 53 inde-energizing the valves 47 (directly 52A and the switch 55A and whichis.

instead of through relay 52) when full brake application is indicated,so that they can test if the corresponding pressures are obtained in thebrake cylinders. The interlock switch guards against the possibilitythat the switch 53 is not operated by the pressure applied to it, e.g.because the pressure has been reduced by leakage, and the valve 47therefore cannot be taken out of its locked up condition for testingpurposes.

Another difference is that an indicator is included to show that thepistons or diaphragms 25 of the brake cylinder 23 have travelled morethan a predetermined amount, indicating for example that the brake shoeshave become overworn and readjustment is necessary. For this purpose thecylinder 23 is provided with ports, indicated by 69, that are uncoveredwhen the pistons or diaphragms have moved the said predetermined amount,whereupon the air under pressure in the cylinder 23 is fed to a switch70 that operates a suitable warning device.

In the circuit of FIGURE 5 the valve outlets 490 no longer lead toatmosphere, but instead are connected to discharge into their respectivebrake cylinders 23, while the valve inlets 470 are now connecteddirectly to the pipe 36 instead of to the pipe connecting the respectivecylinder 33 and the valve 46. The full-on air pressure again is fed to49C and causes the valves 49 to be actuated, but the valves are nowlocked-up under the pressure from the pipe 36, such locking-up beingessentially to prevent re-application of the weights as soon as thebrake pressure from 40 is reduced below the fullon value. The valves 49are now responsive to loss of pressure in the pipe 36 to unlockthemselves and thereafter to apply the weights as soon as they detectafter such interlocking a low enough pressure in the cylinders 23. Ifthe valves 49 release the respective cylinders 33 and 23 are connectedtogether and they may be so constructed that a braking characteristicwithin the permissible limits is obtained. Thus as the weights descendthey will drive air into the brake cylinders 23 and tend to maintain thebraking by the cylinders. This effect will continue until the weightwedge engages the rollers 30 and begins to apply a braking effort of itsown, this braking effort being less than the maximum because of theupward thrust of the air remaining in the cylinders. As the air exhaustsfurther the braking efiort from the air pressure decreasesprogressively, while that from the weights increases progressively, thedesign of the brakes being such that the maximum permissible braking isnot exceeded.

A further additional feature of the circuit of FIGURE 5 is thatadditional braking is available, for example as an emergency measure.This additional braking is provided by supplying the brake cylinderalternatively from the valve 37, or from a similar valve 71 set for anappreciably higher pressure, the pressure that is to be operative beingselected by a valve 72 and indicated by the gauge '57. This necessitatesadditional circuitry in FIG. 6 which may comprise a circuit connectedbetween the lines L and N in which an emergency push button and a hoistcage engaging limit switch are connected in shunt and this combinationis connected in series with the solenoid of the valve 72 in FIG. 5. Withthe valve 72 released air is fed from the valve 37 (in this embodimentset at 60 p.s.i.) to the valves 49, while with the valve actuated, bymanual operation of the emergency pushbutton, or by the hoist cageengaging the hoist cage limit switch, the air is fed instead from thevalve 71 (in this embodiment set at p.s.i.).

It will be noted that in the circuit of FIGURE 5 the priming pressureset by the valve 39 is higher than that of FIGURE 4, the reason for thisis that the spring 27 is stronger to give a faster release and acorrespondingly higher pressure is required for adequate priming.

A brake in accordance with this invention is able to operate faster thanthe hoist brakes known hitherto owing 9 to, among other factors, therelatively low effective masses of the arms 18 and the brake shoes 21and the small distances through which those masses must be moved betweenfull application and full release of the brake.

Moreover, the use as a safety device of a weight acting directly on thebrake arms (i.e. without any intervening linkage) ensures rapidemergency application of the brakes as required, the brake in accordancewith this invention also having the advantage of flexible control of thebraking characteristic provided by the safety device. The braking systemin accordance with this invention is such as to permit rapid operationof the brake. Factors assisting in such rapid operation are the use of arelay valve to supply the operating fluid directly from the supply, theuse of fluid at an initial priming pressure to set up the brake readyfor full braking operation, and the use where possible of an actuatingpressure for the valves (such as valves 45 and 46) lower than the supplypressure so that the time taken for such valves to release is reduced.

It will be understood that the invention has been disclosed withreference to a specific embodiment thereof, and accordingly variousmodifications and changes may be made to the apparatus described withinthe scope of the invention as set out in the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A braking system for a hoist drum mounted for rotation about ahorizontal axis, which system comprises an annular member fixed to andextending from said drum and presenting opposed brake contact surfaces,a pair of brake levers, each of said levers being mounted on an axisintermediate its end for pivotal motion in a plane parallel to the saidhorizontal axis and each of said levers having a brake shoe coupledthereto adjacent one end thereof, said levers being transversely spacedfrom each other and positioned relative to said annular member such thatsaid shoes may be made to engage respectively the opposed contactsurfaces of said annular member by pivotal motion of said levers abouttheir respective axes, a source of fluid pressure, fluid pressureactuated means for pivoting said levers about their respective pivotalaxes to bring said shoes into gripping engagement with said contactsurfaces, valve means connected between said source and said pressureactuated means for controlling the application of pressure from saidsource to said fluid pressure actuated means, spring means acting onsaid levers for maintaining said shoes out of gripping engagement withsaid contact surfaces when fluid pressure below a first predeterminedminimum is applied to said fluid pressure actuated means, a massiveweight mounted for vertical motion on a fluid pressure actuated liftmeans connected to said source of fluid pressure, said weight having infixed relation thereto surfaces inclined with respect to the horizontalbut substantially perpendicular to a plane containing the axes of saidlevers, said surfaces extending above and below said levers and inproximity thereto, portions of said levers having means for hearing onsaid inclined surfaces, said lift means being adapted when actuated tosupport said weight at a predetermined height relative to said leverssuch that the distance between said inclined surfaces at the height ofsaid bearing means is such that the inclined surfaces do not engage thebearing surfaces when said brake shoes are in gripping engagement withsaid annular member wherein upon the pressure applied to said lift meansfalling below a second predetermined minimum said weight falls under theinfluence of gravity and forces the ends of the levers bearing the brakeshoes together to bring the brake shoes into gripping engagement withsaid annular member by means of the interaction between said inclinedsurface and said bearing means.

2. A braking system for a hoist drum mounted for rotation about ahorizontal axis, which system comprises an annular member fixed to andextending from said drum and presenting opposed brake contact surfaces,a pair of brake levers, each of said levers being mounted on an axisintermediate its end for pivotal motion in a plane parallel to the saidhorizontal axis and each of said levers having a brake shoe coupledthereto adjacent one end thereof, said levers being transversely spacedfrom each other and positioned relative to said annular member such thatsaid shoes may be made to engage respectively the opposed contactsurfaces of said annular member by pivotal motion of said levers abouttheir respective axes, a source of fluid pressure, fluid pressureactuated means for pivoting said levers about their respective pivotalaxes to bring said shoes into gripping engagement with said contactsurfaces, valve means connected between said source and said pressureactuated means for controlling the application of pressure from saidsource to said fluid pressure actuated means, spring means acting onsaid levers for maintaining said shoes out of gripping engagement withsaid contact surfaces when fluid pressure below a first predeterminedminimum is applied to said fluid pressure actuated means, a massiveweight mounted for vertical motion between the portions of said leversopposite the mounting axes from these ends of the levers having a brakeshoe coupled thereto, said weight having, in fixed relation thereto,upwardly and outwardly inclined surfaces, said portions of said leversopposite the ends having brake shoe coupled thereto having means forbearing on said inclined surfaces, fluid pressure actuated lift meansconnected to said source of fluid pressure, said lift means beingadapted to support said weight, upon actuation of said lift means, at apredetermined height relative to said levers such that the distancebetween said inclined surfaces at the height of said bearing means isless than the distance between said bearing means when said brake shoesare out of gripping engagement with said annular member, wherein uponpressure to said lift means falling below a second predetermined minimumsaid weight falls under the influence of gravity and forces the ends ofsaid levers apart to bring the brake shoes into gripping engagement withsaid annular member by means of the interaction between said inclinedsurfaces and said bearing means.

3. A braking system for a hoist drum mounted for rotation about ahorizontal axis, which system comprises an annular member fixed to andextending from said drum and presenting opposed brake contact surfaces,a pair of brake levers, each of said levers being mounted intermediateits ends for pivotal motion about a vertical axis, and each of saidlevers having a brake shoe coupled thereto adjacent one end thereof,said levers being transversely spaced from each other and positionedrelative to said annular member such that said shoes may be made toengage respectively the opposed contact surfaces of said annular memberby pivotal motion of said levers about their respective axes, a sourceof fluid pressure, fluid pressure actuated means for pivoting saidlevers about their respective pivotal axes to bring said shoes intogripping engagement with said contact surfaces, valve means connectedbetween said source and said pressure actuated means for controlling theapplication of pressure from said source to said fluid pressure actuatedmeans, spring means acting on said levers for maintaining said shoes outof gripping engagement with said contact surfaces when fluid pressurebelow a first predetermined minimum is applied to said fluid pressureactuated means, a massive weight mounted for vertical motion between theportions of said levers opposite the vertical mounting axes from thoseends of the levers having a brake shoe coupled thereto, said weighthaving, in fixed relation thereto, upwardly and outwardly inclinedsurfaces, said portions of said levers opposite the ends having brakeshoe coupled thereto having means for bearing on said inclined surfaces,fluid pressure actuated lift means connected to said source of fluidpressure, said lift means being adapted to support said weight, uponactuation of said lift means, at a predetermined height relative to saidlevers such that the distance between said inclined surfaces adjacentsaid bearing means is less than the distance between said bearing meanswhen said brake shoes are out of gripping engagement with said annularmember, wherein, upon the pressure to said lift means falling below asecond predetermined minimum said weight falls under the influence ofgravity and forces the ends of said levers apart to bring the brakeshoes into gripping engagement with said annular member by means of theinteraction between said inclined surfaces and said bearing means.

4. In a braking system for a hoist drum mounted for rotation about ahorizontal axis and having mounted thereon an annular member extendingfrom the drum and presenting opposed brake contact surfaces, said systemincluding a pair of brake levers each of which levers is mountedintermediate its ends for pivotal motion about a vertical axis, each ofsaid levers having a brake shoe coupled thereto adjacent one endthereof, said levers being transversely spaced from each other andpositioned relative to said annular member so that said shoes may bemade to engage respectively the opposed contact surfaces of said annularmember upon pivotal motion of said levers about their mounting axes,said system also including a source of fluid pressure and fluid pressureactuated means connected to said source for actuating said levers indirections about their respective pivotal axes to bring said shoes intogripping engagement with said contact surfaces, valve means forcontrolling the application of pressure from said source to said fluidpressure actuated means, and spring means acting on said levers formaintaining said shoes out of gripping engagement with said contactsurfaces when fluid pressure below a first predetermined minimum isapplied through said valve means to said fluid pressure actuated means,the improvement which comprises a massive weight mounted for verticalmotion between the portions of said levers opposite the verticalmounting axes from those ends of the levers having brake shoes coupledthereto, said weight having in fixed relation thereto a pair of opposed,upwardly and outwardly inclined surfaces, means on said portions of saidlevers for bearing on said inclined surfaces, fluid pressure actuatedlift means connected to said source of fluid pressure, said lift meansbeing adapted to support said weight, upon actuation of said liftmeans,at a predetermined height relative to said levers such that the distancebetween said inclined surfaces adjacent said bearing means is less thanthe distance between said bearing means when said brake shoes are out ofgripping engagement with said annular member, wherein, upon the pressureto said lift means falling below a second predetermined minimum saidweight falls under the influence of gravity to a height such that thedistance between the inclined surfaces adjacent the bearing means issubstantially equal to the distance between said bearing means when thebrake shoes are in full gripping engagement with said annular member. 5.A combined pneumatic mechanical braking system for a hoist drumincluding a first pneumatic actuator to operate a mechanical brake onsaid hoist drum producing a first pressure on the brake surfaces inresponse to a first pneumatic pressure supplied to said first pneumaticactuator and a weight operated mechanical actuator to operate said brakeproducing a pressure equivalent to said first pressure on the brakesurface in response to the downward force exerted by the weight, asecond pneumatic actuator opposing the operation of said weight operatedactuator, producing a force equal to said weight in response to apneumatic pressure approximately equal to said first pneumatic pressure,supplied to said first pneumatic actuator, a source of compressed air, afirst control valve movable from an off to a full on position to controlthe pressure of air in the supply line to said first pneumatic actuatorfrom said source, a second control valve movable from a first positionto second position in response to reduction of pressure of said source,said second control valve in its first position coupling said secondactuator to said source and in its second position coupling said secondactuator to said supply line.

References Cited in the file of this patent UNITED STATES PATENTS437,834 Kaseberg Oct. 7, 1890 707,345 Neale Aug. 19, 1902 2,228,818Eksergian Jan. 14, 1941 FOREIGN PATENTS 954,006 Germany Dec. 13, 1956266 Great Britain Ian. 22, 1876 UNITED STATES PATENT OFFICE vCERTIFICATE OF CORRECTION Patent N01, '3,058 547 October l6, 1962 GeraldL, Tiley et alt,

It is hereby certified, that err ent requiring correction and that th orappears in the above numbered patcorrected below,

e said Letters Patent should read as Column 12 line 25,,

for "first" second 9 second occur-rence read Signed and sealed this 18thday of August 1964 (SEAL) Attest:

ERNEsT w. SWIDER' I EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

